1. Field of the Invention
The present invention relates to a water pump. The water pump is mounted on a circulating loop of a cooling water type heat dissipating system so as to drive liquid to flow on the circulating loop to dissipate heat.
2. Description of Related Art
The conventional cooling water type heat dissipating system has two categories. The first conventional cooling water type heat dissipating system is disclosed in Taiwan Utility Model Publication No. 584266. The first conventional cooling water type heat dissipating system comprises a body, a motor and a fan blade. The body has an upper cover, a separating layer and a lower cover, and is formed an enclosed space filled with liquid. The motor and the fan blade are mounted on the enclosed space. The body further comprises an inlet pipe and an outlet pipe which are connected to a loop. When the motor drives the fan blade to rotate, the liquid is driven by the fan blade to flow in the loop so as to dissipate heat.
Taiwan Utility Model Publication No. 587784 discloses the second conventional cooling water type heat dissipating system. The second conventional cooling water type heat dissipating system comprises a shell, a coil assembly and a fan assembly. The shell has an upper cover and a bottom set, and is formed an enclosed space filled with liquid. The fan assembly is mounted on the enclosed space. The shell further comprises an input portion and an output portion which are connected to a loop. The coil assembly is mounted outside of the bottom set. When the coil assembly drives the fan assembly to rotate, the liquid is driven from the input portion to the output portion so as to dissipate heat.
However, in the two patent, there are defects of losing original precision and rotational balance, and they are caused by rubbing the fan blade (or fan) and the upper cover, and then the fan blade (or fan) is worn.
Referring to FIG. 5, it shows the second conventional cooling water type heat dissipating system. The fan 60 has a plurality of fan blades 61 for driving water to flow. Therefore, the velocity of liquid around the fan blades 61 is high, and the velocity of liquid under the fan blades 61 is low owing to the eddy section 63 formed by the eddy effect. The difference of the velocity can cause the pressure difference. That is, when the velocity is high, the pressure is low; and when the velocity is low, the pressure is high. Therefore, the higher pressure under the fan 60 will push the fan 60 upwardly to cause the following two problems, during the period of the rotation:
1. Because the fan 60 is moved upwardly, the fan blades 61 continuously rub the upper cover 62. As a result, the fan blades 61 and the upper cover 62 are worn.
2. If a bottom portion of the shaft of the fan 60 is fixed by a fixed element, the fixed element rub the bearing when the fan 60 is moved upwardly. Accordingly, the bearing is worn.
Besides, the density of the liquid is higher than that of the air, so the pressure difference caused by rotation in the liquid is higher than that in the air. Therefore, in the cooling water type heat dissipating system, the wear of the upper cover and the bearing is faster than that in the air cooling type heat dissipating system. Therefore, it is needed to solve the above problems.